(1). Field of the Invention
This invention relates, in general, to a fixture provided on a rotatable transport member for holding a compact disc while such is being transported from a loading point, to one or more printing locations, and hence to an unloading point. More particularly, the invention relates to a compact disc fixture that can be readily modified for holding compact discs of different diameters and thicknesses.
(2). Description of the Prior Art
In U.S. Pat. No. 5,165,340, which issued on Nov. 24, 1992, and which is entitled Multicolor Printing System For The Silk-Screen Printing Of Compact Discs, there is disclosed a fixture or tooling member for the holding of a compact disc. The fixture is, in general, of one piece and is defined by top and bottom planar surfaces, the bottom surface being supported by the top planar, horizontally disposed, surface of an annular-shaped rotatable transport member. The compact disc fixture is secured to the transport member by conventional threaded fasteners.
The fixture is provided with a circular-shaped well or nest which extends inwardly from the top surface of the fixture for the holding of a compact disc. The depth of the well is such that the top surface of the compact disc, when loaded into the well, is to be in the same plane as, or not more than about 0.003 inch above, the top surface of the fixture. This is of critical importance so that when the top surface of the compact disc is being silk-screen printed the squeegee will engage one continuous surface.
The compact disc fixture in U.S. Pat. No. 5,165,340 is provided also with a bottom, horizontally disposed, circular-shaped well in opposition to the top well, the two wells being separated by a horizontally disposed bridge in which a plurality of openings are provided. This allows communication between the two wells. The bottom well serves as a plenum by means of which vacuum is supplied to the upper or top well through the openings provided in the bridge. This vacuum serves to maintain a compact disc located in the top well, after being registered by an elongated pin raised vertically upwardly so as to intrude into the centerhole of the compact disc, in precise registration for the subsequent silk-screen printing of the top surface of the disc.
Although the compact disc fixture disclosed in U.S. Pat. No. 5,165,340 has functioned quite well in the past for its intended purpose, its use now is, nevertheless, attendant with certain problems and disadvantages. One such disadvantage is that such a disc fixture will accommodate compact discs of only one size, i.e., of only one diameter and thickness. This restriction has presented no particular problem, in the past, in the case of the diameter, as compact discs have been of only one diameter. More recently, however, compact discs have been made available of not only 120 mm diameter, but also of a number of other smaller or larger diameters, and of various thicknesses.
Thus, to allow for the silk-screen printing of any of these compact discs or any other sizes of discs to emerge in the market place, those in the business of printing compact discs must maintain an inventory of disc fixtures of various diameters so that whichever diameter compact discs are to be printed, the transport member can be provided with fixtures having a top well or nest of the needed diameter. This, however, is a costly proposition. The rotatable transport member in a compact disc printing apparatus may have, in general, as many as thirty or more fixtures mounted on it. Moreover, not only is it expensive to maintain a complete inventory of fixtures of different diameters, the replacement of a disc fixture having a compact disc nest of one diameter on the transport member with one of a different diameter is a labor intensive operation. This naturally leads to increased and undesirable overhead costs. The replacement of a compact disc fixture on a transport member with one of a different diameter requires, in general, that the fixture being replaced be disconnected from the transport member, e.g., by removal of the threaded fasteners. The replacement fixtures must then each be fastened to the transport members by the same threaded fasteners removed.
Another disadvantage with the use of compact disc fixtures such as disclosed in U.S. Pat. No. 5,165,340 results from the fact that, on occasion, the top surface of the fixture becomes damaged, e.g., by gouges or burrs in the top surface. When this occurs, the compact disc fixture must be replaced with another fixture; otherwise, the surface of the compact disc will not be uniformly printed or the silk screen may be damaged. The fixture that is replaced is no longer of any value and is discarded. Overtime, a large number, if not all, of the compact disc fixtures initially provided on the rotatable transport member of a silk-screen printing apparatus may need be replaced. This, of course, leads to increased costs of operation to the silk-screen printer operator.
Compact discs of somewhat different thicknesses, on the other hand, have always presented a problem in the silk-screen printing, offset printing, or other methods of printing of the top surface of the disc. This results from the fact that compact discs received by a printer from different molding machines or molds may be of slightly different thicknesses. As a matter of fact, even with a single source of compact discs, where the compact discs are molded on different apparatus, the thicknesses of the compact discs from the different apparatus may be somewhat different. Also, new disc technologies for video discs and writable and multi-layer discs dictate thicknesses which are different than that of conventional audio compact discs.
It is, of course, critical that the thickness of a compact disc correspond with the depth of the top well of the disc fixture being used in the printing operation. This is critically necessary, as above-mentioned, so that the squeegee on a silk-screen printing head, or print head on an offset print head, or other process head will meet a continuous planar surface in its travel. Where a batch of compact discs are encountered by a printer operator having a thickness different, i.e., greater or less, from that of the depth of the top well of the fixtures on the printing apparatus to be used, the compact disc fixtures may need be replaced. Otherwise, the compact disc surface may not be suitably printed. This, of course, means the replacement of thirty or so disc fixtures with fixtures having a top well of the required depth.
Thus, it can readily be seen that there is need for a compact disc fixture that is capable of readily accommodating compact discs of different diameters and thicknesses, and in an economical manner.